Migration departures from starling roosts

Abstract

Migration departures from Southern Ontario roosts of the European starling (Sturnus vulgaris) have frequently been observed by radar. Departures occurred at the normal time for roost dispersals. The birds usually moved northeast in spring and southwest in autumn, but occasional reverse movements were detected. Most of the sites from which departures were recorded produced normal dispersals and departures on more than one morning. In both spring and autumn, departures in both normal and reverse directions occurred with following winds. In spring, departures in the normal direction occurred with above normal temperatures; in autumn, they occurred with below normal temperatures. When only cases with following winds were considered, these temperature correlations were maintained. No correlation between incidence of departures and temperature change, wind speed, amount of cloud, or relative humidity was detected.